This invention pertains to color laser imaging methods and apparatus and, in particular, to methods and apparatus for indicating a low toner condition in color laser imaging devices.
Color printing by an electrophotographic printer is achieved by first scanning a digitized image onto a photoconductor. Typically, the scanning is performed with diodes which pulse a beam of energy onto the photoconductor. The diodes can be, for example, laser diodes or light emitting diodes (LEDs). The photoconductor typically comprises a movable surface coated with a photoconductive material capable of retaining localized electrical charges. In many cases, the movable surface is in the form of a revolvable cylindrical drum.
The surface of the photoconductor is divided into small units called pixels. The photoconductor is generally configured to continuously revolve such that any given pixel is repeatedly moved past the diodes at a substantially regular cycle and at a substantially constant rate, and along a substantially fixed path relative to the diodes. Each pixel is capable of being charged to a given electrical potential, independent of the electrical charge of each surrounding pixel.
During operation of the printer, substantially all of the pixels are first charged to a base electrical charge as they move past a charging unit during each revolution of the photoconductor. Then, as the pixels move past the diodes, the beam of energy, such as a laser, is either directed at, or not directed at, each of the pixels as dictated by the digital data used to pulse the laser. If the laser is directed at a given pixel, the given pixel can be electrically altered by changing (typically discharging) the base electrical charge to a second electrical charge.
Thus, after passing a laser during operation of the printer, a first portion of the pixels will remain at the base electrical charge because they were not exposed to the laser, while a second portion will have a different charge because of being altered by the laser. The first and second portions of unaltered and altered pixels thus form an image on the photoconductor. One portion of pixels will attract toner, while the other portion will not, depending on various factors such as the electrical potential of the toner. That is, the unaltered pixels will either attract or not attract toner, and vice versa with regard to the altered pixels.
Once the toner has been applied to the photoconductor, the toner is then transferred to a finished product medium, such as a sheet of paper. Although the finished product medium typically comprises paper, it can also comprise other materials such as plastic, as in the case of a transparency. The transfer of toner from the photoconductor to the finished product medium can be direct, or it can be indirect using an intermediate transfer device. That is, in the direct method, the toner is transferred directly from the photoconductor to the finished product medium. In the indirect method, the toner is transferred first to an intermediate transfer device, and then transferred from the intermediate transfer device to the finished product medium. The intermediate transfer device typically comprises a revolvable endless belt. During operation of the printer, the intermediate transfer device typically moves by circulating, or revolving, past the photoconductor.
After the toner is transferred to the finished product medium, it is processed to fix the toner thereto. This last step is normally accomplished by thermally heating the toner to fuse it to the finished product medium, or applying pressure to the toner on the finished product medium. Any residual toner on the photoconductor and/or the intermediate transfer device is then removed by a cleaning station, which can comprise either or both mechanical and electrical means for removing the residual toner.
A variety of methods are known for selectively attracting toner to a photoconductor. Generally, each toner has a known electrical potential affinity. As described above, selected pixels of the photoconductor can be exposed by a laser from a base potential to a given potential associated with the selected toner, and then the toner can be presented to the photoconductor so that the toner is attracted only to the selectively exposed pixels. This latter step is known as developing the photoconductor.
In some processes, after the photoconductor is developed by a first toner, the photoconductor is then recharged to the base potential and subsequently exposed and developed by a second toner. In other processes, the photoconductor is not recharged to the base potential after being exposed and developed by a selected toner. In yet another process, the photoconductor is exposed and developed by a plurality of toners, then recharged, and then exposed and developed by another toner. In certain processes, individual photoconductors are individually developed with a dedicated color, and then the toner is transferred from the various photoconductors to a transfer medium which then transfers the toner to the finished product medium. The selection of the charge-expose-develop process depends on a number of variables, such as the type of toner used and the ultimate quality of the image desired.
Image data for an electrophotographic printer (which will also be known herein as a xe2x80x9cprinterxe2x80x9d), including color laser printers, is digital data which is stored in computer memory. The data is stored in a matrix or xe2x80x9crasterxe2x80x9d which identifies the location and color of each pixel which comprises an overall image. The raster image data can be obtained by scanning an original analog document and digitizing the image into raster data, or by reading an already digitized image file. The former method is more common to photocopiers, while the latter method is more common to printing computer files using a printer. Accordingly, the invention described below is applicable to either photocopiers or printers.
Recent technology has removed the distinction between photocopiers and printers such that a single printing apparatus can be used either as a copier, a printer for computer files, or a facsimile machine. In any event, the image to be printed onto finished product media is provided to the printer as digital image data. The digital image data is then used to pulse the beam of a laser in the manner described above so that the image can be reproduced by the electrophotographic printing apparatus. Accordingly, the expression xe2x80x9cprinterxe2x80x9d should not be considered as limiting to a device for printing a file from a computer, but should also include any device capable of printing a digitized image in the general manner described herein, regardless of the source of the image.
The image data file is essentially organized into a two dimensional matrix within the raster. The image is digitized into a number of lines. Each line comprises a number of discrete points. Each of the points corresponds to a pixel on the photoconductor. Each point is assigned a value representing data pertaining to its color and potentially other attributes, such as density. The matrix of points makes up the resultant digitally stored image. The digital image is stored in computer readable memory as a raster image. That is, the image is cataloged by line, and each line is cataloged by each point in the line. A computer processor, or digital hardware, reads the raster image data line-by-line, and actuates the laser to selectively expose a given pixel based on the presence or absence of coloration, and the degree of coloration for the pixel.
The method of transferring the digital raster data to the photoconductor via a laser, lasers, or LEDs, is known as the image scanning process, or the scanning process. The scanning process is performed by a scanning portion, or scanning section, of the electrophotographic printer. The process of attracting toner to the photoconductor is known as the developing process. The developing process is accomplished by the developer section of the printer. Image quality is dependent on both of these processes. Image quality is thus dependent on both the scanning section of the printer, which transfers the raster data image to the photoconductor, as well as the developer section of the printer, which manages the transfer of the toner to the photoconductor.
In the case of a typical multi-color laser printer, at least one laser scanner is included and utilized to generate a latent electrostatic image on the photoconductor. Generally, one latent electrostatic image is generated for each color plane to be printed. A xe2x80x9ccolor planexe2x80x9d generally refers to a portion of the output image which comprises only a single color of toner. For example, in a four-color laser printer, the final output image comprises four color planes. This allows for each of four colors to be imaged first onto a photoconductor, then transferred onto an intermediate transfer device, and finally transferred from the intermediate transfer device to the finished product medium.
In general, multi-color printers are configured as four-color printers. The four color planes typically printed, and which are generally considered as necessary to generate a relatively complete palate of colors, are yellow, magenta, cyan and black. That is, the typical color printer is provided with toners in each of these four colors. These colors will be known herein as the xe2x80x9cprimary colorsxe2x80x9d. Some printers have the capability of printing one color on top of another on the same pixel, so as to generate a fuller palate of finished colors.
In a typical scanning process, a laser is scanned from one edge of the photoconductor to the opposite edge while being selectively pulsed in accordance with the image data file. That is, the laser scans across the photoconductor, following a row of pixels. As the laser scans along the row of pixels, it is selectively pulsed a pixel-by-pixel basis. That is, for each pixel in a row, the laser is either directed at the pixel, or not directed at it. The scan of the laser in this manner causes a line of point which make up the digital image to be transferred from the raster onto the photoconductor. As the photoconductor moves past the laser, the laser advances to the next row of pixels, and the next line of points from the digital image is scanned by the laser onto the photoconductor. The image data is thus scanned onto the photoconductor in a pixel-by-pixel and line-by-line basis until the complete image is transferred to the photoconductor.
The side-to-side scanning action of each laser is traditionally accomplished using a dedicated multi-faceted rotating polygonal mirror at which a stationary laser is aimed. The rotation or the mirror causes the reflected laser beam to be scanned across the photoconductor at a unique relative lineal position from a first edge to a second edge of the photoconductor. As the mirror rotates to an edge of the polygon between facets, the reflected laser reaches the edge of the photoconductor. When the laser is reflected off of the next facet as it rotates into position, the laser is essentially reset to the first edge of the photoconductor to begin scanning a new line onto the advancing photoconductor.
Generally, there are two types of color laser printers. One type is the multi-pass printer and the other type is the in-line printer. The multi-pass type of laser printer, also known as the four-pass, is generally provided with a single photoconductor and a single laser/mirror scanner system. The four-pass type is also generally provided with a movable intermediate transfer device, commonly in the form of an endless belt which circulates, or revolves, past the photoconductor. In operation, each of the four color planes (typically black, yellow, cyan, and magenta) which make up an output image is consecutively developed on the photoconductor and completely deposited on the intermediate transfer device. That is, as a first color plane is developed on the photoconductor, it is deposited in its entirety, as toner, on the intermediate transfer device as the device makes a complete first revolution, past the photoconductor.
The intermediate transfer device then begins a second revolution past the photoconductor during which the second color plane is developed on the photoconductor and deposited in its entirety on the intermediate transfer device in registered alignment with the first color plane. This process is repeated in like manner for the third and fourth color planes until all four color planes have been deposited on the intermediate transfer device so as to build-up the completed image thereon. It is important that each succeeding color plane is deposited exactly xe2x80x9con top ofxe2x80x9d the previous color plane. That is, each succeeding color plane is superimposed, or deposited in registration with, the previous color plane. After the image has been completed with all four color planes on the intermediate transfer device, the image is then transferred to a sheet of finished product medium.
The toner is generally in the form of a fine powder. Each color of toner is contained in a dedicated compartment to avoid mixing of the different color toners prior to deposition of the toners on the photoconductor. The toner compartments are usually configured as cartridges which are removable from the printer apparatus. The removable nature of the cartridges facilitates resupply of the toner. That is, when the level of toner in a given toner cartridge becomes low, or when the cartridge becomes empty, the cartridge can be removed from the printer and replaced by another like cartridge which contains a supply of the same color toner.
As mentioned above, the in-line type of printer generally has a photoconductor and a laser/mirror scanner system of each color toner. Thus, a typical in-line printer will include four photoconductors and four laser/mirror scanner systems, wherein each of the laser/mirror scanner systems correspond to one each of the photoconductors. The photoconductors are usually situated xe2x80x9cin-linexe2x80x9d relative to one another, and proximate to the intermediate transfer device. Each of the photoconductor-laser/scanner combinations is dedicated to producing a given color plane. For example, a particular photoconductor-laser/scanner combination can produce only yellow color planes, while another photoconductor-laser/scanner combination can produce only magenta color planes.
Prior art printer apparatus have been equipped with low toner detection systems which can detect and identify a low toner condition. These low toner detection systems have been configured to identify the specific toner cartridge which is empty, or which has a low level of toner. Various methods of detecting a low level of toner in a toner cartridge are known and need not be discussed herein.
In order to communicate the low toner condition to the user or operator, prior art printer apparatus have relied on a graphics display interface. That is, prior art printer apparatus have been equipped with a display screen on which the low toner condition, and the specific toner cartridge needing replacement, is identified in the form of text or graphics. Unfortunately, this type of graphics display interface can add considerable complexity to the printer apparatus. Additionally, other prior art printer apparatus have been produced without a graphics display interface in an effort to reduce the complexity of the printer. However, in these latter types of prior art printers the toner cartridge which has a low toner condition is not identified. Thus, in these latter types of prior art printers, the user must physically check each toner cartridge for a low toner condition. This can result in an unacceptable amount of time spent by the user in identifying the low toner cartridge, and can also result in an incorrect identification which, in turn, results in the wrong cartridge being replaced. It is therefore desirable to find a less complex, yet reasonably reliable means of communicating a low toner condition to the user of a color laser printer.
The invention includes methods and apparatus for identifying a toner cartridge having a low toner condition in a multi-toner printer apparatus, and for presenting a toner cartridge having a low toner condition in a printer apparatus to the user of the apparatus.
In accordance with one embodiment of the present invention, an apparatus for identifying a toner cartridge having a low toner condition in a printer is disclosed. The apparatus comprises a movable carriage for supporting a plurality of toner cartridges. The carriage can be in the form of a substantially rotary carousel. The apparatus also comprises a cartridge access way through which one of the plurality of toner cartridges can be accessed. The apparatus causes a cartridge having a low toner condition to be accessible at the access way by moving the carriage so that the low toner cartridge is positioned at the access way for removal and replacement. The apparatus can be configured to position the low toner cartridge at the access way only at times when the printer is idle.
In accordance with another embodiment of the present invention, an apparatus for identifying a toner cartridge having a low toner condition in a printer is disclosed, wherein the apparatus comprises a movable carriage for supporting a plurality of toner cartridges. The carriage can be configured to remove in a substantially linear manner as apposed to a rotational manner as in the above embodiment. The apparatus causes a cartridge having a low toner condition to be accessible at the access way by moving the carriage so that the low toner cartridge is positioned at the access way for removal and replacement. As in the above, embodiment, the apparatus can be configured to position the low toner cartridge at the access way only during times when the printer is idle.
In accordance with yet another embodiment of the present invention, an apparatus for identifying a toner cartridge having a low toner condition is disclosed, wherein a plurality of toner cartridges are supported in a substantially fixed manner. The apparatus comprises a plurality of cartridge access ways, wherein each one of the cartridge access ways corresponds to one each of the toner cartridges. The apparatus can also comprise a plurality of doors, wherein each one of the doors is configured to cover one each of the cartridge access ways. Alternatively, or in addition, the apparatus can comprise a plurality of visual signal devices, wherein each one of the signal devices corresponds to one each of the cartridge access ways. A low toner cartridge can be identified by causing one of the doors to open, thus presenting the low toner cartridge to the user. Alternatively, one of the visual signal devices can be caused to generate a visual signal, thus identifying to the user a low toner cartridge. The apparatus can be configured to continue printing output images after the low toner cartridge has been identified.
In accordance with still another embodiment of the present invention, a method of presenting a low toner cartridge to the user of a printer is disclosed. The method includes providing a cartridge access way, detecting a low toner condition in a toner cartridge, and causing the low toner cartridge to become accessible through the cartridge access way. The method can also include the step of positioning the low toner cartridge to the cartridge access way. The low toner cartridge can be positioned at the cartridge access way only at times when the printer is idle.